Impact of Grazing Intensities on Community Biodiversity and Productivity of Alpine Grassland in Qinghai Lake Region

The impact of different grazing intensities on biodiversity and productivity of alpine grassland in Qinghai lake region was investigated using comparative sampling plots.The relationship between plant species diversity and productivity was explored through two years continuous grazing trials.Results showed that species richness and diversity index had a single peak change with the increase of grazing intensity.Species diversity was supreme under moderate grazing intensity.Species richness,diversity index and evenness index were minimum under high grazing intensity.Along with the increase of grazing intensity,community productivity decreased(P0.05).The aboveground biomass of cyperaceous plant was not significantly different between different grazing intensities,whereas the productivities of gramineous plant and leguminous plant significantly decreased(P0.05).The yield ratios of both gramineous plant and leguminous plant decreased,whereas the yield ratios of both cyperaceous plant and weeds increased with the increase of grazing intensity.There were significantly unimodal functional relationships between aboveground productivity and Alatalo evenness index,and Simpson diversity index(R2=0.910,P=0.027;R2=0.953,P=0.010).Therefore,grazing intensity is an important factor to affect species diversity and productivity.